In 2013 the London Subway, with 402 km the second longest subway system on earth after Shanghai, celebrated its 150th anniversary without being widely celebrated as a ground-breaking engineering event

Today, mass transit systems like subways have become indispensable for urban passenger transport. Their numbers have risen continuously since 1863, from Istanbul to Paris, Berlin, Boston, Los Angeles, New York, Tokyo, Moscow etc.

It is impossible to imagine how modern cities, suffering from chronic traffic congestion, would be able to function without subways. Today, 190 subway systems of different size operate in 54 countries.

These numbers are bound to grow in the coming decades to meet rapidly expanding traffic in growing urban areas where more than two thirds of global population – some six billion people (!)- will live by the middle of the century.

Every day some six billion people will then need to travel from their homes to their workplaces, compared to less than four billion today. Buses, let alone cars, alone cannot do that job, considering the sheer volumes of human masses to be moved and the lack of urban space. In the absence of well-functioning mass transit systems, very frequent traffic breakdowns will be the inevitable consequence. The bigger the cities the more pressing the problems. Mega-cities with more than 10 million inhabitants that already today house 10 per cent of the global population will be the worst hit.

One can take a look as of today what it means for a multimillion city like Dhaka, which devotes only 7 per cent of its surface to roads (25 per cent being the standard), to function without effective mass transport systems: intolerable traffic jams and dis-functioning of the economic urban life.

Future prospects will be particularly bleak in emerging countries, most of which already lack functioning urban infrastructure.

Singapore and Hong Kong as well as European cities like Stockholm, Amsterdam, Copenhagen, Vienna, Paris, Zurich, London, Munich, Berlin and Stuttgart, which have invested a lot of efforts in developing efficient systems, are among the positive examples from which to take lessons.

All developing countries will have to pay infinitely more attention to long-term urban planning. Many cities, having missed the optimal timing, will have to tear down large urban areas, build more roads to complement mass transit systems, put up more sky-scrapers or even put a brake on further population growth.

The amount of investments necessary will be colossal, easily € 50 billion for a five-million city needing a 100 km rail-system. Most cities will be unable to finance such gigantic projects on their own. Central governments and international finance institutions will have to offer long-term loans; and governments will have no choice but to impose heavy taxes on motor vehicles.

It is urgent to wake up to the huge traffic challenges of an urban global society. Too much time has been lost by negligent governments, with far too much public money wasted on subsidies, corruption and armies. To meet the mobility challenge countries and cities will have to establish much closer cooperation.

Developed countries and cities will have to help. But the sheer volume of the global financial needs exceeds by far the financial capacities of the shrinking populations in the affluent regions of the world.